Estrogen Dependent Growth of a Rat Pituitary Tumor (MtT/F84)

Abstract

An estrogen dependent transplantable pituitary tumor, designated MtT/F84, was induced in an estrogenized female F344 rat and has been serially passaged in 17 β-estradiol treated female rats. It grew well in rats treated with estrone, 17 β-estradiol (E2) or estriol but not in ovariectomized females or in rats given progesterone or testosterone. Growth of MtT cells about 105 when mixed with 1.1 or 11 μg grafted site of E2 in vitro and grafted into s.c., were much enhanced of their growth compared with the same number of MtT cells similarly grafted without E2 on the other side of breast chain in same ovariectomized rat. This local growth promoting effect of E2 on MtT was inhibited by the subsequent injection of tamoxifen at grafted site. Nuclear estrogen receptor (ER) levels correlatively increased according to the administered doses of E2, but cytosolic ER reversely decreased with the increase of E2 administration.